问题
选择题
The country's railway system has launched online ticket-booking and a real-name ticket purchasing system, and _______ requires passengers to provide their ID numbers when buying tickets.
A．which
B．that
C．what
D．this
答案
答案：B
本题考查代词。题干中and已是连词，不要其它连词。此处that是代词，用来指代前面句子的内容。